Raster Source

Demonstrates pixelwise operations with a raster source.

This example uses a ol/source/Raster to generate data
based on another source. The raster source accepts any number of
input sources (tile or image based) and runs a pipeline of
operations on the input pixels. The return from the final
operation is used as the data for the output source.

In this case, a single tiled source of imagery is used as input.
For each pixel, the Vegetation Greenness Index
(VGI)
is calculated from the input pixels. A second operation colors
those pixels based on a threshold value (values above the
threshold are green and those below are transparent).